Well Ive owned my 2006 4.6L STX for 10 years now. 120K trouble free miles later, I would like to upgrade to a newer F-150. Ive been so happy with the 4.6L being such a reliable motor, I havn't had a single mechanical issue. In fact the only issue Ive had with the truck itself were the vacuum hubs that failed at about 85K.

Looking into a 2015-2018 F-150. I tow a 6K boat regularly but not very long distances. I hope to own my next F-150 for upwards of 10 years just like my 4.6L. MPG isn't the most important thing to me. I want reliability (priority #1) and towing ability (priority #2).

So, 3.5L Ecoboost or 5.0L V8?

 

2017 F150 with the 5.0
It is the last year before the 10 speed tranny took over all f150's and the 5.0 seems to be as bullet proof as the 4.6. I still have both, the 5.0 runs rings around the 4.6, in speed, gas mileage, etc. Kinda the turtle and the hare. They both get the job done at their own pace.

 

5.0 with 6 speed.

 

You're looking for the 5.0 V8 with the 6 speed auto as stated above. If you were happy with the power of the anemic 4.6, you'll love the 5.0. The EB engines are the power makers but get horrible gas mileage town driving with most getting around 13 mpgs. Hiway they do great at over 20 mpgs and some at 25. The newer trucks with the 10 speed auto have been a headache. Seems to be no rhyme or reason that the 10 speed auto just starts with false neutral, hard shifting, no shifting, locked in a gear, just all kinds of issues. It can happen when new, it can happen at over 50,000 trouble free miles. Ford apparently can't fix them either which is the bad part.

 

I went from an '04 with the 4.6 that like you I never had any issues with to a '15 with the 5.0. The 5.0 is way more engine than the 4.6, but I get better mileage (19 mpg around town to 21-22 highway) and it's a blast to drive. I would look for one with the 6 speed trans and the sleeved cylinders. The newer versions have a 10 speed that some have had problems with and plasma coated cylinders which have issues with oil consumption.

If you're not looking for lots more engine than the 4.6, the non-turbo 6 cyl that is offered is very reliable and still more powerful than the old 4.6.

 

You can’t go wrong with 2016 with the. 5.0 and the six speed trans, love mine! Three years has been me replacement rotation, I’m going to keep this one for a few more years!